Nominations would open immediately and close in early February. Ballot papers would be sent to members in late February with voting in March, turning the Lib Dem spring conference into a hustings event.

Mr Kennedy resigned on Saturday, days after admitting he had a drink problem.

His resignation came after 25 MPs said they would refuse to serve under him.

'Man of substance'

Sir Menzies has the backing of more than a third of Lib Dem MPs, plus grandees including Lord Ashdown.

Lord Ashdown told BBC Radio 4's Today programme: "At the next election he'll offer the British public an alternative that provides weight and substance and seriousness in a political debate that is, frankly, increasingly obsessed with modishness and flim-flam."

It is very important that we have a debate about the direction of the party